High efficiency fan blades with airflow-directing baffle elements

ABSTRACT

Fan blades are provided that increase aerodynamic and operational efficiency, and which include baffle elements positioned on the distal ends of the fan blades. The baffle elements operate by shearing blade tip vortices, thereby minimizing turbulent fluid effects, and further providing fluid shunt that imparts a radial velocity component to the fluid. The baffle elements produce a more focused and collimated fluid flow perpendicular to the plane of rotation during forward rotation, and produce a more diffuse, radially-outward directed fluid flow during reverse rotation. The baffle elements are positioned such that they are characterized by a first angle with respect to the radial axis of the fan blade and a second angle with respect to the low pressure surface of the fan blade.

TECHNICAL FIELD

The present invention relates generally to fan blades and, moreparticularly, to fan blades with airflow-directing baffle elementsdisposed thereon.

BACKGROUND OF THE INVENTION

The purpose of a fan is to move fluid continuously against moderatepressures. As used herein, the term fluid is intended to indicatematerial in a liquid, gaseous or vapor state. Accordingly, fan operationis highly dependent upon the total static pressure generated to overcomeambient fluid pressures and create fluid flow. An operating fan producesa pressure rise across the unit because the rotating fan blades functionas aerofoils.

A moving aerofoil is essentially a flat plate inclined at an angle andmoving through air or other fluids. The aerofoil experiences a forceexerted thereon, which is resolvable to a component parallel to thedirection of motion (drag) and a component perpendicular to thedirection of motion (lift). In a fan, the rotating fan blades experiencedrag in the direction opposite that of rotation, and experience liftperpendicular to the plane of rotation. The lift forces produced on thehigh pressure surface of the aerofoil fan blade generate a dischargepressure that results in volume flow of fluid from the surface.

The performance of a fan in terms of pressure, volume flow, fluidvelocity, power, and efficiency depends on a number of factors, the mostcritical of which are:

(a) the design and type of fan;(b) the size of the fan;(c) the speed of rotation of the fan impeller;(d) the condition of the fluid passing through the fan; and(e) the geometry of the fan blades comprising the impeller.Consequently, it is a goal of fan design to develop fan blade geometriesthat optimize operating characteristics and performance.

There are four common types of fans: centrifugal fans, cross-flow fans,propeller fans, and axial-flow fans. As used herein, the term “impeller”or “fan impeller” is intended to indicate a rotating set of bladesdesigned to impart motion to a mass of fluid. Centrifugal, orradial-flow, fans include an impeller running in a casing having aspirally shaped contour. The fluid enters the impeller in an axialdirection and is discharged at the periphery, with the impeller rotationbeing toward the casing outlet. The amount of work done on the fluid,evident in the pressure development of the fan, depends primarily on theangle of the fan blades with respect to the direction of rotation at theperiphery of the impeller. Three main forms of blades are commonly: (1)backward bladed, in which the blade tips incline away from the directionof rotation; (2) radial bladed, where the blade tips are radiallydisposed; and (3) forward curved, where the blade tips incline towardthe direction of rotation.

Most centrifugal fan impellers have shrouded blades as part of a fanwheel. The shrouds include annular plates that are fitted at each end ofthe blades, giving mechanical strength to the fan impeller and reducingleakage between blades and casing. Fluid leakage around fan impellerblades and between blades and fan casings substantially reduce fanefficiency, requiring more power for a given total fan pressure orvolume flow.

Cross-flow, or tangential, fans have impellers with blades shaped likeforward-curved centrifugal fan impellers. However, both ends of theimpeller in a cross-flow fan are sealed and it is fitted into a casingin which fluid enters at the periphery on one side, passes through theimpeller, and leaves from the periphery at the other side. The axes ofthe inlet and outlet are roughly perpendicular; therefore, the flowthrough a cross-flow fan is curved rather than diametral. Cross-flow fanblades are generally of rectangular shape and considerable length,disposed in a parallel longitudinal orientation, forming a cylindricalimpeller comprised of blades that allow for the curved fluid flow paththrough the impeller unit.

Propeller fans are comprised of a motor driven sheet metal impeller,positioned in an orifice with relatively large clearance. Fluid flowthrough a propeller fan is analogous to flow through an orifice ratherthan strict linear/axial flow. Propeller fans and axial flow fans aregenerally analogous in terms of structure and the fluid mechanics ofoperation, and are equivalent for most applications.

Axial flow fans are those where the flow of the fluid is substantiallyparallel to the axis of the impeller hub. Axial flow fans can be placedin three primary categories: (1) fluid circulator, or free fan; (2)diaphragm-mounted fan; or (3) ducted fan. A free fan is one that rotatesin a common unrestricted fluid space, for example, desk, wall, pedestal,and ceiling fans. Diaphragm-mounted fans transfer fluid from onerelatively large space to another, as for example an exhaust orventilation fan that drives fluid from a factory or warehouse to theexternal atmosphere, or alternatively, drives outside fluid into an openinternal area or transfers fluid between inside areas. Diaphragm-mountedfans do not use ductwork or fine-clearance cylindrical casings. Ductedfans constrain fluid flow in an axial direction with an enclosing shroudor duct. The minimum duct length required to satisfy the ductedcondition must be in excess of the axial distance between inlet to, andoutlet from, the impeller blades.

Generally, fluid approaches the fan impeller on the low pressure inletside in an axial direction and leaves from the high pressure outlet sidewith an axial and rotational component due to work done by the impellertorque. Since the purpose of a fan is to move fluids against ambientpressures, the rotational velocity component is disadvantageous becauseit reduces the available total pressure generated by a fan to producevolume flow in an axial direction.

Notwithstanding the numerous fan designs developed to maximize fanefficiency while minimizing noise, vibration, and cost, a number ofproblems still exist in fan design for which adequate solutions have yetto be developed. For example, like centrifugal fans, axial flow andpropeller-type fans suffer from fluid leakage around the fan impellerblade tips, and between blade tips and fan casings, which substantiallyreduces fan efficiency, requiring higher rotational impeller speeds andmore power to produce a given total fan pressure or volume flow. Thisproblem is characterized in that the fluid passing through the fanreverses direction at the blade tips, flows around the blade tips fromthe outlet surface to the inlet surface in a countercurrent fashion, andlowers efficiency as fluid discharged from the high pressure side bleedsback to the low pressure side creating vortices, stall conditions, andother turbulent flow characteristics, and further increasing undesirablenoise and vibration.

An additional problem with conventional fan blades, for example,circular arc, flat undersurface, elliptical, and planar blades, is therotational velocity component imparted to the fluid due to the torque ofthe fan blades. This component can decrease fan efficiency by decreasingthe amount of available total static pressure on the discharge side, andas a result, decreasing the total volume flow for a given impeller speedand configuration. While conventional methods exist to reduce thisproblem, for example, upstream or downstream guide vanes andcontra-rotating assemblies, these methods possess attendant problems oftheir own, including, for example, increased noise and powerrequirements.

Moreover, conventional fan blades are not capable of redirecting therotational velocity component to create a radial component, which ineffect would push residual fluid flow (i.e. fluid flow that is not in anaxial direction) in a radial direction and would form a more collimatedand laminar volume flow from the fan unit.

An additional problem with conventional fan blades in axial flow andpropeller-type fan systems is the clearance space on the low pressuresuction/inlet side required to achieve acceptable operating performance.In particular, axial flow and propeller-type fans need sufficientclearance between the low pressure side of the blades and an adjacentsurface, for example a solid and continuous wall or ceiling, in order toachieve efficient flow-through performance. If an impeller assembly islocated too closely adjacent to a solid and continuous surface,turbulent flow characteristics such as stalls and vortices develop onthe suction surface of the impeller blades. This poses a problem inareas of limited space, for example, in rooms with low ceilings orlimited floor space, where it would be advantageous to achieve maximalfluid flow while minimizing the dead space behind the low pressuresuction side of any fan units.

Accordingly, it would be desirable to provide a fan blade configurationthat increases fan efficiency (increased total static fan pressure andvolume flow at lower impeller speeds and lower power requirements),decreases noise and vibration, and creates a more focused and collimatedvolume flow.

BRIEF SUMMARY OF THE INVENTION

The present invention is generally directed toward improved fan bladeswhich reduce, minimize, or eliminate countercurrent fluid bleeding,blade tip vortices, stalling effects, turbulent flow conditions, lowpressure suction/inlet side clearance space, noise, vibration, and therotational fluid velocity component, and further which increase theradial fluid velocity component and overall fan efficiency.Fluid-directing blade structures (described hereinafter as “baffles” or“baffle elements”) are disposed at the distal end (i.e., the tip end) ofthe fan blades provided herein. The baffle elements are positioned onthe distal end of each fan blade, directed toward the low pressuresuction/inlet side, the high pressure discharge/outlet side, or both,and further at a first specified angle with respect to the radial axisof the fan blade, a second specified angle with respect to the lowpressure surface of the fan blade, and/or at a third specified anglewith respect to the high pressure surface of the fan blade.

In one embodiment, the present invention is directed toward fan bladesincluding a blade body having a leading edge, a trailing edge, aproximal end, a distal end, a high pressure surface, a low pressuresurface, and a radial axis, and a baffle element, such that the baffleelement is positioned on the distal end of the blade body at a firstangle with respect to the radial axis, at a second angle with respect tothe low pressure surface, and/or at a third angle with respect to thehigh pressure surface.

In another embodiment, the present invention is directed toward fanblades including a blade body having a leading edge, a trailing edge, aproximal end, a distal end, a high pressure surface, a low pressuresurface, and a radial axis, and a baffle element, such that the baffleelement is positioned on the distal end of the blade body and extendingfrom the low pressure surface at an angle of approximately 45-degreeswith respect to the radial axis, and at an angle of approximately90-degrees with respect to the low pressure surface.

In yet another embodiment, the present invention is directed towardaxial-flow fans including a drive mechanism, a hub rotatably coupled tothe drive mechanism, a plurality of fan blades, and a baffle elementattached to at least one of the high pressure surface, the low pressuresurface, or both of at least one blade of the plurality of blades at thedistal end of the blade, such that the blades are attached to the hub atthe proximal ends, and positioned such that the distal ends project in asubstantially radial direction away from the hub, and such that thebaffle element is positioned on the distal end at a first angle withrespect to the radial axis, at a second angle with respect to the lowpressure surface, and/or at a third angle with respect to the highpressure surface of the blade.

Other features and advantages will be apparent from the followingdescription, including the drawings, and from the claims set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

The various described embodiments will hereinafter be described inconjunction with the appended drawings provided to illustrate and notlimit the described embodiments, wherein like designations denote likeelements, and in which:

FIG. 1 is a side view parallel to the plane of rotation of aconventional propeller or axial flow type fan illustrating fluid flowcurrents when operating in forward rotation;

FIG. 2 is a bottom or front view, orientation depending, of aconventional propeller or axial flow type fan illustrating peripheraltip vortices;

FIG. 3 is a side view parallel to the plane of rotation of a fan withbaffle elements according to non-limiting embodiments of the presentinvention illustrating fluid flow currents when operating in forwardrotation;

FIG. 4 is a bottom or front view, orientation depending, of a fan withbaffle elements according to non-limiting embodiments of the presentinvention;

FIG. 5 is a side view parallel to the plane of rotation of aconventional propeller or axial flow type fan illustrating fluid flowcurrents when operating in reverse rotation;

FIG. 6 is a side view parallel to the plane of rotation of a fan withbaffle elements according to non-limiting embodiments of the presentinvention when operating in reverse rotation;

FIG. 7 is view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 8 is a view perpendicular to the plane of rotation of an assemblyof fan blades according to non-limiting embodiments of the presentinvention;

FIG. 9A is a side view parallel to the plane of rotation of an assemblyof fan blades according to non-limiting embodiments of the presentinvention, FIG. 9B is a view perpendicular to the plane of rotation ofthe assembly depicted in FIG. 9A;

FIG. 10 is a side view parallel to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 11A is a partial view parallel to the plane of rotation of a baffleelement according to non-limiting embodiments of the present invention,FIG. 11B is a partial view to the plane of rotation of a baffle elementaccording to non-limiting embodiments of the present invention;

FIG. 12 is a view parallel to the plane of rotation of a baffle elementaccording to non-limiting embodiments of the present invention;

FIGS. 13A, 13B, and 13C are views parallel to the plane of rotation ofassemblies of fan blades according to non-limiting embodiments of thepresent invention;

FIG. 14A and FIG. 14B are views perpendicular to the plane of rotationof fan blades according to non-limiting embodiments of the presentinvention;

FIG. 15 is a view parallel to the plane of rotation of a baffle elementaccording to non-limiting embodiments of the present invention;

FIG. 16A is a view parallel to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention. FIG. 16Bis a view perpendicular to the plane of rotation of the fan bladedepicted in FIG. 16A;

FIG. 17A is a view parallel to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention. FIG. 17Bis a view perpendicular to the plane of rotation of the fan bladedepicted in FIG. 17A;

FIG. 18 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 19 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 20 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 21 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 22 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 23 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention;

FIG. 24 is a view perpendicular to the plane of rotation of a fan bladeaccording to non-limiting embodiments of the present invention; and

FIG. 25 is a side view of an axial-flow fan according to non-limitingembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The described embodiments provide improved fan blades for reducing,minimizing, or eliminating countercurrent fluid bleeding, blade tipvortices, stalling effects, turbulent flow conditions, low pressureinlet/suction side clearance space, noise, vibration, and the rotationalfluid velocity component, and further for increasing the radial fluidvelocity component and overall fan efficiency.

Before various embodiments are explained in detail, it is to beunderstood that the described embodiments are not limited in applicationto the construction and arrangement of the structures, components,steps, and/or examples set forth in the following description orillustrated in the drawings. The described embodiments are capable ofother forms and may be carried out in various ways. Also, it isunderstood that the phraseology and terminology used herein is forpurpose of description and should not be regarded as limiting.

As used herein, the term “forward rotation” is intended to indicate thedirection of rotation of a fan impeller such that the discharge surfacecorresponds to the forward-facing side of the impeller. For example, ina ceiling fan application, the orientation of the pitch of the blades issuch that forward rotation would produce fluid flow down into the spacebelow the fan, while alternatively, reverse rotation would produce fluidflow up through the fan impeller and into the space above the fan. Thereis no convention in the art defining forward or reverse rotation aseither clockwise or counterclockwise rotation. Designers of fansdetermine what direction of rotation is forward rotation by setting theorientation of the blade pitch on a fan impeller and setting which sideof the impeller is the forward-facing side. The fan blades disclosedherein are capable of application regardless of the respectivedirections of rotation. However, for purposes of illustration, and notto be regarded as limiting, forward rotation corresponds to clockwiserotation and reverse rotation corresponds to counterclockwise rotationof the fan impellers illustrated in FIGS. 2, 4, 7, 8, 9B, 14A, 14B, 16B,17B, 18, 19, 20, 21, and 22, which are front views of the forward-facingsides of the illustrated fan blades and fan impellers.

FIG. 1 illustrates a conventional fan blade assembly 10 in forwardrotation, and the fluid flow currents associated therewith. Duringoperation, the forwardly-rotating blades 20 generate lower pressure onthe inlet/suction surface 22 and higher pressure on the outlet/dischargesurface 23. The low pressure surface 22 induces influx of fluid into therotating blades 20, while the high pressure surface 23 forces volumeflow 25 from the blades. Due to the pressure gradient across therotating blades 20, a portion of the volume flow from the high pressuresurface 23 bleeds back, around the tips of the fan blades, to the lowpressure surface 22, producing vortex currents 24.

The vortices 24 produced by the rotating blades 20 reduce the totalstatic pressure generated by the fan, and therefore reduce the volumeflow 25 for given operating conditions (i.e., given power input andblade rotational speed). The vortices 24 produced by the rotating blades20 further disrupt the volume flow in the annular region formed by thecircular path of the tip portion of blades 20, as illustrated in FIG. 2rotating in the direction indicated by arrow 60. The disrupted fluidregion includes vortices 24, which can induce the formation of stallconditions (not shown), which are large secondary rotational fluid flowsalong the length of the low pressure surface 22 of the fan blade 20.These turbulent fluid flow characteristics substantially reduce theefficiency of conventional fan blades.

As illustrated in FIG. 3, the baffle elements 150 according to variousembodiments of the present invention increase fan blade efficiency byredirecting the fluid in the tip region of rotating blades 100. Theredirection of the fluid by the baffle elements 150 locally increasesthe pressure on the low pressure surface 122 at the distal tip region 58of the fan blade 100, thereby locally reducing the pressure gradientacross the fan blade at the distal tip region 58 relative to thepressure gradient across the fan blade 100 proximally from the distaltip region 58. Baffle element 150 further provides a barrier to preventthe formation of vortices around the blade tip. As illustrated in FIG.4, this reduces the fluid turbulence in the annular region 59 formed bythe path of the tip portion of rotating blades 100. The reduction ofvortices and other turbulent effects decreases the prevalence of stallconditions on the low pressure surface 122 of the rotating blades 100.

The baffle element 150 additionally shunts fluid in the directionindicated by arrow 57 in FIG. 4. The shunt imparts a radial velocitycomponent to the fluid adjacent to the side of the rotating fan bladeson which baffle element 150 is positioned. When the baffles 150 arepositioned on the low pressure surface 122 of the fan blade, the radialvelocity component directs fluid radially inward to the low pressureside of the rotating blade assembly, where it is worked upon by theblades 100 and discharged from the high pressure outlet surface 123. Inthis mode, the fan blade 100 with baffle element 150 has two propulsionareas: the high pressure outlet surface 123 and the surface of thebaffle element 150. The radial shunt of the fluid due to the propulsionarea of baffle element 150 partially offsets the efficiency losses dueto the rotational component of the fluid discharged from the highpressure outlet surface 123 due to the torque of rotating fan blades100. The combined vortex shearing and fluid-shunting due to the baffleelements 150 results in a more focused and collimated volume flow 125.Accordingly, the baffle elements 150 increase the available static fanpressure and volume flow for given operating conditions, and function asflow directing elements.

By way of example, and not intended as limiting, in fan applicationswhere the fan can be operated in forward and reverse, the vortices thatare produced by conventional fan blades are a substantial problemregardless of the direction of blade rotation. Various embodiments ofthe present invention provide baffle elements that function to increasefan efficiency and performance during operation in both forward andreverse directions.

FIG. 5 illustrates a conventional fan blade assembly 10 in reverserotation, and the fluid flow currents associated therewith. Duringoperation, the reversely-rotating blades 20 generate lower pressure onthe bottom-facing surface and higher pressure on the top-facing surface.The low pressure surface 22 induces influx of fluid 30 from below intothe rotating blades 20, while the high pressure surface 23 dischargesvolume flow from the blades 20. A portion of the volume flow from thehigh pressure surface 23 bleeds back, around the tips of the fan blades,to the low pressure surface 22 producing vortex currents 24 due to thepressure gradient across the rotating blades 20.

As illustrated in FIG. 6, the baffle elements 150 redirect the fluid inthe distal tip region 58 reducing, minimizing, or eliminating thevortices and flow disruptions in the periphery of the impeller area asin the case with forward rotation. However, in reverse rotation, thebaffle elements shunt fluid in an outward radial direction. In thismode, the baffle elements 150 redirect at least a portion of thevelocity component in the discharge flow from high pressure surface 123into an outwardly radial component 134.

The effect of the baffle elements 150, as illustrated in FIGS. 3 and 6respectively, is that in forward rotation, the baffle elements 150 arepositioned on the low pressure surface 122 and produce a more denselyfocused and collimated discharge volume flow 125 approximatelyperpendicular to the plane of the fan impeller, whereas in reverserotation, the baffle elements 150 are positioned on the high pressuresurface 123 and produce a more radially-distributed discharge volumeflow 134 approximately parallel to the plane of the fan impeller.

FIG. 7 is a view perpendicular to the plane of rotation of a fan blade100 according to non-limiting embodiments of the present invention. Theblade 100 rotates in forward rotation in the direction indicated byarrow 60 and the view is of high pressure surface 123. Blade 100 isattached to hub 160 at the proximal end 140 of the blade. Blade 100 iscomprised of blade body including distal end 130, leading edge 10,trailing edge 120, and radial axis A. Radial axis A designates areference line originating at the center point of hub 160 and projectingin a radial direction, indicated as direction B in FIG. 7, through thebody of blade 100. Positioned on the distal end 130 of blade 100 isbaffle element 150. Baffle element 150 is positioned such that it formsan angle 170, indicated as θ, with respect to radial axis A of blade100.

FIG. 8 is a view perpendicular to the plane of rotation of an assembly105 of fan blades according to non-limiting embodiments of the presentinvention. The fan blades 100 rotate in forward rotation in thedirection indicated by arrow 60. Each blade 100 is attached to hub 160at the proximal end 140 of the blade. Each blade is further comprised ofdistal end 130, leading edge 110, trailing edge 120, radial axis A, andbaffle elements 150 positioned on the distal ends 130 of the blades 100forming angle 170 with respect to radial axis A. In this embodiment,leading edge 110, tailing edge 120 and radial axis A are substantiallyparallel. The blade and hub assembly 105 of FIG. 8 depicts four baffledfan blades attached to hub 160. It is understood that fan assembliesaccording to non-limiting embodiments of the present invention are notlimited to any number of fan blades or baffled fan blades, and couldinclude any number of baffled fan blades as part of an impeller or fanblade assembly suitable for the particular purposes and operatingconditions of the fan.

FIG. 9A is a side view parallel to the plane of rotation of an assemblyof fan blades according to non-limiting embodiments of the presentinvention. FIG. 9B is a view perpendicular to the plane of rotation ofthe assembly depicted in FIG. 9A. The baffle elements 150 are attachedto fan blades 100 at their distal ends. The fan blades 100 are attachedto hub 160 at their proximal ends. Leading edge 110 and trailing edge120 are indicated in both FIGS. 9A and 9B.

FIG. 10 is a side view parallel to the plane of rotation and along thelength of a fan blade 100 according to non-limiting embodiments of thepresent invention. The baffle element 150 is positioned on the distalend of the blade 100 extending from the low pressure surface 122. Baffleelement 150 is positioned such that it forms an angle 200, indicated asφ, with respect to the low pressure surface 122.

The baffle element 150 is depicted extending from the low pressuresurface 122 in FIGS. 10, 11A, 13A, and 15. However, the positioning ofthe baffle element 150 is not limited to extension from the low pressuresurface 122 of the fan blade, and can be positioned to extend from thehigh pressure surface 123, as depicted in FIG. 11B, or from both the lowpressure surface 122 and the high pressure surface 123, as depicted inFIG. 12. In embodiments where baffle element 150 is positioned such thatit extends from both the low pressure surface 122 and the high pressuresurface 123, the baffle element forms a third angle 250, indicated as λin FIG. 12, with respect to the high pressure surface 123.

As used herein, the term “approximately” to describe angle values indegrees is interpreted to encompass the stated value ±10-degrees. Also,it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In embodiments where the baffle element 150 extends from the lowpressure surface 122 of the fan blade, the angle 200 ranges fromapproximately 0-degrees to approximately 180-degrees, preferably fromapproximately 45-degrees to approximately 135-degrees, and is mostpreferably 90-degrees. See, for example, FIGS. 10, 11 and 15. Inembodiments where the baffle element 150 extends from the high pressuresurface 123, the angle 200 ranges from approximately 180-degrees toapproximately 360-degrees, preferably from approximately 225-degrees toapproximately 315-degrees, and most preferably is approximately270-degrees. In embodiments where the baffle element 150 extends fromboth the low pressure surface 122 and the high pressure surface 123, thesecond angle 200 ranges from approximately 0-degrees to approximately180-degrees, preferably from approximately 45-degrees to approximately135-degrees, and most preferably is approximately 90-degrees; and thethird angle 250 ranges from approximately 0-degrees to approximately180-degrees, preferably from approximately 45-degrees to approximately135-degrees, and most preferably is approximately 90-degrees. Inembodiments where the baffle element 150 extends from both the lowpressure surface 122 and the high pressure surface 123, the second angle200 and the third angle 250 may be equal or different.

The first angle 170 formed between the baffle element 150 and the radialaxis A of the fan blade can range from approximately 0-degrees toapproximately 180-degrees, preferably from approximately 30-degrees toapproximately 60-degrees, and most preferably is approximately45-degrees.

FIGS. 13A, 13B, and 13C depict fan blade assemblies where the baffleelements 150 respectively extend from the low pressure surface 122, thehigh pressure surface 123, and both the low pressure surface 122 and thehigh pressure surface 123.

Baffle element 150 can be integrally formed as part of fan blade 100 asdepicted in FIGS. 7 through 15. An integrally formed fan blade (i.e., amonolithic structure including the body of the blade and the baffleelement), according to certain embodiments of the present invention, canbe fabricated from any one of the numerous common solid componentmanufacturing methods well known to those of ordinary skill in the art,including, but not limited to, die casting, injection molding, sheetstamping, extrusion molding, and CNC machining. In addition to thebaffle being integrally formed with the fan blade into a monolithiccomponent, the baffle element 150 can be fabricated as a separatecomponent 300, which is structured and configured to be fastened orattached, either permanently or removably, from the correspondinglystructured and configured fan blade 375, as depicted in FIGS. 16A and16B. The baffle element component 300 can be attached to the fan blade375 at junction 350 by any means known to one of ordinary skill in theart, including, but not limited to, compression mechanisms, rivets,bolts, screws, other fasteners, adhesives, epoxies, and welds.

Baffle element 150 can further be manufactured as an appliance,attachment, or add-on component 400, which can be attached, permanentlyor removably, to a conventional fan blade 475. In this manner, a baffleelement can be applied to a conventional fan blade as a retrofit. Asillustrated in FIGS. 17A and 17B, the baffle appliance 400 is structuredand configured to mate with and attach to conventional fan blade 475 atjunction 450. The appliance 400 can be used to convert conventional fansinto more efficient fans by utilizing the baffle element according tovarious embodiments of the present invention.

The baffle elements have been illustrated in the drawings and describedherein as planar rectangular fin or winglet type structures 150. It isto be understood, however, that the baffle elements are not limited torectangular or square shapes, but may be fabricated in any number ofshapes including, but not limited to, rectangular, square, trapezoidal,rhomboidal, quadrilateral, triangular, elliptical, circular,semi-circular, pentagonal, hexagonal, heptagonal, and octagonal.Additionally, the baffle elements are not limited to planar structures,and may be fabricated in convex, concave, or other three-dimensionalgeometries. Moreover, the baffle elements 150 are not limited to thewidth of the fan blade, and may be structured and positioned such thatthey run shorter than (FIG. 18) or exceed (FIGS. 20 through 22) theleading edge 110 and/or the trailing edge 120 of any particular fanblade.

The baffle elements of the present invention have heretofore beendescribed in conjunction with planar, rectilinear blades. However, thebaffle elements of the present invention are applicable to any of theconventional types of fan blades, including, but not limited to,circular arc, flat undersurface, elliptical, and planar blades. Thebaffle elements are further applicable to propeller-type fan blades andany conventional axial-flow fan blade geometry. For example, and withoutlimitation, FIGS. 18 through 21 depict a swept-blade configuration witha baffle element 150 positioned on the distal end 130 at an angle 170with respect to radial axis A, and extending from the low pressuresurface at a second angle of approximately 90-degrees. Dashed line 180in FIGS. 18 and 20 depicts the outline of the edge of a conventionalswept fan blade. In various embodiments of the present invention, theportions of the blade within line 180 and baffle element 150 may beconfigured analogously to a conventional fan blade, wherein the bladeterminates at the distal end. In such embodiments, baffle element 150extends from the low pressure surface, the high pressure surface, orboth, intersecting the conventional swept blade proximal to the distalend. An embodiment where the baffle element intersects a rectilinear fanblade proximal to the distal edge is illustrated in FIG. 22.

In various embodiments of the present invention, the portions of theblade within line 180 and baffle element 150 are eliminated. In suchembodiments, the fan blades terminate at the baffle element, which isdirectly positioned on the distal end as illustrated in FIGS. 19 and 21.

The fan blades have been illustrated and described herein as includingat least one baffle element, wherein the baffle element is positioned onthe distal end of the fan blade or is positioned at an intermediatelocation proximally with respect to the distal end. In variousembodiments, the fan blades may include a plurality of baffle elements.For example, FIG. 23 illustrates a fan blade according to embodiments ofthe present invention wherein two baffle elements 150 and 151 arepositioned on the blade body. The two baffle elements 150 and 151 arepositioned on the blade body at first angles 170 and 171, respectively,with respect to radial axis A. The angles 170 and 171 may be of the samevalue or of different values. The baffle elements 150 and 151 may be ofthe same shape, size and configuration or of different shapes, sizes andconfigurations. The second angles (not shown) between the baffleelements 150 and 151 and the low pressure surface may be of the samevalue or of different values for each respective baffle elementpositioned on the blade body.

FIG. 23 depicts baffle element 150 positioned on the distal end 130 ofthe blade body and baffle element 151 positioned proximal from thedistal end. Fan blades according to various embodiments are not limitedto this configuration. For example, FIG. 24 depicts baffle elements 150and 151, where both baffle elements are positioned proximal from thedistal end 130.

The fan blades according to various embodiments of the present inventionare not limited to any particular number of baffle elements, and caninclude any number of baffle elements suitable for the particularapplication of the fan blades. Moreover, regardless of the number ofbaffle elements per blade and their positioning on the blade body, thebaffle elements may be manufactured as an appliance, attachment, oradd-on component, which can be attached, permanently or removably, to aconventional fan blade. In this manner, baffle elements can be appliedto a conventional fan blade as retrofits.

The baffle elements of the present invention can be incorporated intonew fan designs, used as modifications to existing fan designs, orapplied as retrofits of existing conventional propeller and/oraxial-flow fans. The baffle elements are particularly suited for, butnot limited to, use in axial-flow or propeller type fan units such asfluid circulator fans, free fans, diaphragm-mounted fans, propellerfans, and ducted fans.

Fan blades according to various embodiments of the present invention areapplicable to common fan units including, but not limited to desk fans,wall fans, floor fans, window fans, pedestal fans, ceiling fans, boxfans, ventilation fans, and industrial fans. For example, in ceiling fanapplications, as illustrated in FIG. 3, baffle elements 150 reduce theamount of open space necessary between the ceiling and the rotatingblades 100 in order to achieve optimal fluid volume flow-through 125,maximizing convectional cooling. Baffle elements 150 are alsoadvantageous when a ceiling fan is operated in reverse rotation, asillustrated in FIG. 6, where baffle elements 150 produce a radial shunt134 that efficiently distributes fluid throughout a room, rather thancreating localized turbulent effects, for example vortices 34 in FIG. 5,common to conventional fan blades. This reduction in low pressure sidespace is particularly advantageous for rooms with low ceilings, where aconventional ceiling fan would be impractical.

An additional example of a non-limiting embodiment of the presentinvention would be a large-scale industrial or mobile box fan positionedwith a vertical plane of rotation. Such fans conventionally requiresignificant free space on the low pressure suction/inlet side in orderto achieve optimal volume flow. The baffle elements according tonon-limiting embodiments of the present invention allow such fans todevelop optimal volume flow with reduced low pressure side free space atmoderate rotational speeds, whereas conventional fans would requiresubstantially higher fan speeds and increased power consumption toachieve comparable flow.

An exemplary fan unit 500 according to various embodiments of thepresent invention is illustrated in FIG. 23. Fan unit 500 includes adrive mechanism 510, for example a direct current (DC) or a pulse widthmodulated (PWM) motor; a hub 160 rotatably coupled to the drivemechanism 510; and a plurality of fan blades 100, at least one of whichincludes a baffle element 150. The methods in which the components arefabricated and assembled, and the incorporation of additional componentsinto the unit, for example control means, support structures, andcasings or housings, are the subject of design or engineering choice,the exercise of which does not take the fan unit outside the scope ofthe present invention.

Advantages of embodiments of the present invention additionally includenoise reduction, because turbulent flow conditions that create noise arereduced, minimized, or eliminated; and the aerodynamic efficiency of thefan blades are increased because the baffle elements provide for radialfluid direction and shunting toward the low pressure inlet, providingfor increased fluid volume flow and increased static total pressure forthe same fan speed, size, and power requirements.

While the present invention has been described in terms of fans and fanblades, which traditionally operate in air environments, it is to beunderstood that the baffle elements according to various embodiments areapplicable to other fluid handling equipment and fluid systemsincluding, but not limited to, compressors and gas turbines, and liquidhandling systems, for example propeller-type water conveying equipment.

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for purposes of clarity, other elements, such as, for example, detailsregarding specific hardware components generally associated with fanequipment. Those of ordinary skill in the art will recognize that thespecific fan equipment of interest will dictate the type, configuration,and positioning of the fan unit and dimensioning of components. However,because the technical details and functionality of such elements arewell known in the art and because they do not facilitate a betterunderstanding of the present invention, a detailed discussion of suchelements is not provided herein.

While several embodiments of the invention have been described, itshould be apparent, however, that various modifications, alterations andadaptations to those embodiments may occur to persons skilled in the artwith the attainment of some or all of the advantages of the disclosedinvention. Therefore, this application is intended to cover all suchmodifications, alterations and adaptations without departing from thescope and spirit of the disclosed invention as defined by the appendedclaims.

1. A fan blade comprising: a blade body including a leading edge, atrailing edge, a proximal end, a distal end, a high pressure surface, alow pressure surface, and a radial axis; and at least one baffle elementpositioned on the blade body at a first angle with respect to the radialaxis and at a second angle with respect to the low pressure surface. 2.The fan blade of claim 1, further comprising a plurality of baffleelements positioned on the blade body at a first angle with respect tothe radial axis and at a second angle with respect to the low pressuresurface.
 3. The fan blade of claim 1, wherein the at least one baffleelement is positioned on the distal end.
 4. The fan blade of claim 1,wherein the first angle with respect to the radial axis is in the rangeof approximately 30-degrees to approximately 60-degrees.
 5. The fanblade of claim 1, wherein the first angle with respect to the radialaxis is approximately 45-degrees.
 6. The fan blade of claim 1, whereinthe at least one baffle element extends from the low pressure surface.7. The fan blade of claim 1, wherein the second angle with respect tothe low pressure surface is approximately 90-degrees.
 8. The fan bladeof claim 1, wherein the at least one baffle element extends from boththe low pressure surface and the high pressure surface.
 9. The fan bladeof claim 8, wherein the second angle with respect to the low pressuresurface is approximately 90-degrees, and a third angle between thebaffle element and the high pressure surface is approximately90-degrees.
 10. The fan blade of claim 1, wherein the at least onebaffle element extends from the high pressure surface.
 11. The fan bladeof claim 1, wherein the second angle with respect to the low pressuresurface is approximately 270-degrees.
 12. The fan blade of claim 1,wherein the at least one baffle element is configured to be removablyattached to the blade body.
 13. The fan blade of claim 1, wherein theblade is utilized in an assembly comprising a plurality of fan blades.14. A fan blade comprising: a blade body including a leading edge, atrailing edge, a proximal end, a distal end, a high pressure surface, alow pressure surface, and a radial axis; and at least one baffle elementpositioned on the distal end of the blade body at a first angle ofapproximately 45-degrees with respect to the radial axis and extendingfrom the low pressure surface at a second angle of approximately90-degrees with respect to the low pressure surface.
 15. A fan bladecomprising: a blade body including a leading edge, a trailing edge, aproximal end, a distal end, a high pressure surface, a low pressuresurface, and a radial axis; and a plurality of baffle elements eachpositioned on the blade body at a first angle with respect to the radialaxis and at a second angle with respect to the low pressure surface. 16.An fan comprising: a hub; a plurality of blades, each blade comprising aleading edge, a trailing edge, a proximal end, a distal end, a highpressure surface, a low pressure surface, and a radial axis, and eachblade attached to the hub at the proximal end and positioned such thatthe distal end projects in a substantially radial direction away fromthe hub along the radial axis; and a plurality of baffle elementsattached to the plurality of blades and positioned at a first angle withrespect to the radial axis and at a second angle with respect to the lowpressure surface.
 17. The fan of claim 16, wherein the baffle elementsare positioned on the distal ends of the fan blades.
 18. The fan ofclaim 16, wherein the baffle elements are attached to the low pressuresurfaces of the blades.
 19. The fan of claim 16, wherein the first anglewith respect to the radial axis is approximately 45-degrees and thesecond angle with respect to the low pressure surface is approximately90-degrees.
 20. A baffle element configured to be retrofit to a fanblade, the fan blade comprising a leading edge, a trailing edge, aproximal end, a distal end, a high pressure surface, a low pressuresurface, and a radial axis, wherein the baffle element is configured tobe positioned on the fan blade at a first angle with respect to theradial axis and at a second angle with respect to the low pressuresurface.